Infrasonics Program

Infrasonics is the study of sound below the range of human hearing.
These low-frequency sounds are produced by a variety of geophysical processes including earthquakes, severe
weather, volcanic activity, geomagnetic activity, ocean waves, avalanches, turbulence aloft,
and meteors and by some man-made sources such as aircraft and explosions.

Infrasonic and near-infrasonic sound may provide advanced warning and monitoring of these extreme
events.

We are engaged in the development and deployment of infrasonic instruments
for detection and monitoring of low-frequency sound generated by several
important anthropogenic and geophysical processes. A strong focus is on
hazardous geophysical phenomena in order to improve basic knowledge and
early warnings. We have demonstrated that avalanches in the Rocky
Mountains can be detected and located using an infrasonic array on the
plains near Boulder. Using a similar array, we demonstrated that tornadoes
on the high plains can be detected several minutes before they touch down,
thus demonstrating a valuable tool to provide advanced warning for
residents in tornado-prone regions. We conduct theoretical studies of
infrasonic source mechanisms in order to optimize systems for detection and
identification. The object of one study is the correlation between
infrasound, sprites, and other transient, luminescent phenomena associated
with severe weather. Another study involves methods to reduce audible noise
(such as along highways) using both active and passive techniques.
We typically collaborate with other organizations within NOAA, other
government agencies, universities, and foreign scientists. For example,
we are participating in a cooperative study with Armenian
scientists researching earthquake precursors, and the we have been
requested to assist with the Nuclear Test Ban treaty monitoring system.
We also collaborate with other research groups in field
experiments, e.g., involving Radio Acoustic Sounding System (RASS) and
Lidar. Potential research and development include: infrasound observations
from Peacewing
platforms, infrasound measurements of other planetary
atmospheres, and ocean wave generated infrasound with a focus on tsunami
detection.